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LTC4064

sn4064 4064fs

APPLICATIO S

FEATURES

TYPICAL APPLICATIO

DESCRIPTIO

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File Servers, RAID Systems

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Storage Products

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Li-Ion Battery Back-Up

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Preset 4V Charge Voltage with 1% Accuracy

Prolongs 4.2V Li-Ion Battery Lifetime

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Automatic Recharge

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Thermal Regulation Maximizes Charging Rate

without Risk of Overheating*

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No MOSFET, Sense Resistor or Blocking Diode

Required

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Programmable Charge Termination Timer

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Thermistor Input for Temperature Qualified Charging

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Programmable Charge Current with 7% Accuracy

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C/10 Charge Current Detection Output

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25µA Supply Current in Shutdown Mode

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Charge Current Monitor Useful for Gas Gauging*

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Charges Directly from USB Port

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Tiny Thermally Enhanced 10-pin MSOP Package

Monolithic Linear Charger

for Back-Up Li-Ion Batteries

The LTC4064 is a standalone linear charger optimized for

prolonging the life of 1-cell Li-ion batteries in battery back-

up applications. By charging to a float voltage of 4V

instead of 4.2V or 4.1V, the LTC4064 decelerates the aging

process and capacity degradation when the battery is

unused for long periods of time but must be in a ready

state.

An external capacitor programs a safety timer to terminate

the charge cycle while the charge current is set externally

with a single resistor. When the input supply is removed,

the LTC4064 automatically enters a low current sleep

mode, dropping the battery drain current to less than 3µA.

Additional safety features designed to maximize battery

lifetime and reliability include NTC temperature sensing

and low battery charge conditioning (trickle charging).

The IC contains an on-chip power MOSFET and eliminates

the need for an external sense resistor and blocking diode.

The LTC4064 also includes C/10 detection circuitry, AC

present logic, and fault detection circuitry.

, LTC and LT are registered trademarks of Linear Technology Corporation.

BAT

PROG

TIMER

NTCGND

1.5k

4.7µF

0.1µF

BAT

= 1A

4064TA01

SHDN

1-CELL

Li-Ion

BATTERY*

*AN OUTPUT CAPACITOR MAY BE REQUIRED

DEPENDING ON BATTERY LEAD LENGTH

= 5V

FLOAT

= 4V

8 2

5, 11

LTC4064

Standalone Back-Up Li-Ion Battery Charger

*US Patent No. 6522118

Summary of content (16 pages)

PAGE 1
LTC4064 Monolithic Linear Charger for Back-Up Li-Ion Batteries U FEATURES DESCRIPTIO ■ The LTC4064 is a standalone linear charger optimized for prolonging the life of 1-cell Li-ion batteries in battery backup applications. By charging to a float voltage of 4V instead of 4.2V or 4.1V, the LTC4064 decelerates the aging process and capacity degradation when the battery is unused for long periods of time but must be in a ready state.
PAGE 2
LTC4064 U W W W ABSOLUTE AXI U RATI GS U W U PACKAGE/ORDER I FOR ATIO (Note 1) Input Supply Voltage (VCC) ..................................... 10V BAT ......................................................................... 10V NTC, SHDN, TIMER, PROG ............ –0.3V to VCC + 0.3V CHRG, FAULT, ACPR ................................ –0.3V to 10V BAT Short-Circuit Duration .......................... Continuous BAT Current (Note 2) ............................................. 1.
PAGE 3
LTC4064 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 5V SYMBOL PARAMETER CONDITIONS MIN TYP VPROG PROG Pin Voltage RPROG = 3k, IPROG = 500µA ICHRG CHRG Pin Weak Pulldown Current VCHRG = 1V 30 50 µA VCHRG CHRG Pin Output Low Voltage ICHRG = 5mA 0.35 0.6 V VACPR ACPR Pin Output Low Voltage IACPR = 5mA 0.35 0.6 V VFAULT FAULT Pin Output Low Voltage IFAULT = 5mA 0.
PAGE 4
LTC4064 U W TYPICAL PERFOR A CE CHARACTERISTICS Battery Regulation Voltage vs Battery Charge Current 4.02 Battery Regulation Voltage vs Temperature VCC = 5V TA = 25°C RPROG = 3k 4.01 4.010 4.02 4.008 4.00 4.006 3.99 3.96 3.94 3.92 3.98 3.88 50 100 150 200 250 300 350 400 450 500 IBAT (mA) 4.000 3.998 3.994 VCC = 5V RPROG = 3k IBAT = 10mA 3.97 0 4.002 3.996 3.90 3.96 3.86 –50 3.992 3.
PAGE 5
LTC4064 U W TYPICAL PERFOR A CE CHARACTERISTICS PROG Pin Voltage vs Charge Current 1.515 1.515 1.6 VCC = 5V TA = 25°C RPROG = 3k 1.4 PROG Pin Voltage vs Temperature Constant Current Mode PROG Pin Voltage vs VCC Constant Current Mode VBAT = 3.5V TA = 25°C RPROG = 3k 1.510 VCC = 5V VBAT = 4V RPROG = 3k 1.510 1.505 0.8 0.6 VPROG (V) 1.505 1.0 VPROG (V) VPROG (V) 1.2 1.500 1.500 1.495 1.495 1.490 1.490 0.4 0.2 1.485 0 0 50 100 150 200 250 300 350 400 450 500 CHARGE CURRENT (mA) 4 4.
PAGE 6
LTC4064 U U U PI FU CTIO S CHRG (Pin 1): Open-Drain Charge Status Output. When the battery is being charged, the CHRG pin is pulled low by an internal N-channel MOSFET. When the charge current drops to 10% of the full-scale current, the N-channel MOSFET latches off and a 30µA current source is connected from the CHRG pin to ground. The C/10 latch can be cleared by grounding the SHDN pin, momentarily, or toggling VCC.
PAGE 7
LTC4064 W W SI PLIFIED BLOCK DIAGRA VCC 2 – 105°C D1 TA D2 + TDIE M2 ×1 D3 M1 ×1000 + – MA 9 30µA NTC 6 BAT R1 NTC MP + VA – CA R2 + – 2.485V REF HOT COLD DISABLE CHRG 1 STOP SHDN 8 SHDN C/10 R3 30µA 1.5V LOGIC ACPR 10 R4 ACPR 0.15V + C2 C/10 FAULT 3 R5 – FAULT CHARGE COUNTER C3 OSCILLATOR – 2.
PAGE 8
LTC4064 U OPERATIO The LTC4064 is a linear battery charger designed primarily for charging single cell lithium-ion batteries used in backup applications. With a 4V final float voltage accuracy of ±1%, the LTC4064 maximizes the lifetime of 4.2V chemistry lithium-ion batteries. A precision, automatic recharge feature ensures that the battery voltage remains within 100mV of this 4V float voltage at all times.
PAGE 9
LTC4064 U W U U APPLICATIO S I FOR ATIO Undervoltage Lockout (UVLO) An internal undervoltage lockout circuit monitors the input voltage and keeps the charger in shutdown mode until VCC rises above the undervoltage lockout threshold. The UVLO circuit has a built-in hysteresis of 200mV. Furthermore, to protect against reverse current in the power MOSFET, the UVLO circuit keeps the charger in shutdown mode if VCC falls to within 35mV of the battery voltage.
PAGE 10
LTC4064 U W U U APPLICATIO S I FOR ATIO Programming The Timer The programmable timer is used to terminate the charge cycle. The timer duration is programmed by an external capacitor at the TIMER pin. The total charge time is: Table 1. FAULT CHRG High Low Charge cycle has started, C/10 has not been reached and charging is proceeding normally. Low Low Charge cycle has started, C/10 has not been reached, but the charge current and timer have been paused due to an NTC out-oftemperature condition.
PAGE 11
LTC4064 U W U U APPLICATIO S I FOR ATIO V+ VDD VCC 7/8 VCC 8 VCC 400k LTC4064 CHRG 3 – RHOT 1% 2k TOO COLD + µPROCESSOR OUT NTC IN 4064 F03 RNTC 10k TOO HOT – Figure 3. Microprocessor Interface full-scale current (C/10), the N-channel MOSFET is turned off and a 30µA current source is connected to the CHRG pin. The IN pin will then be pulled high by the 2k pull-up. By forcing the OUT pin to a high impedance state, the current source will pull the pin low through the 400k resistor.
PAGE 12
LTC4064 U W U U APPLICATIO S I FOR ATIO NTC Trip Point Errors When a 1% resistor is used for RHOT, the major error in the 50°C trip point is determined by the tolerance of the NTC thermistor. A typical 10k NTC thermistor has a ±10% tolerance. By looking up the temperature coefficient of the thermistor at 50°C, the tolerance error can be calculated in degrees centigrade. Consider the Vishay NTHS0603N02N1002J thermistor which has a temperature coefficient of –3.3%/°C at 50°C.
PAGE 13
LTC4064 U W U U APPLICATIO S I FOR ATIO Regardless of mode, the voltage at the PROG pin is proportional to the current being delivered to the battery. Power Dissipation The conditions that cause the LTC4064 to reduce charge current due to the thermal protection feedback can be approximated by considering the power dissipated in the IC.
PAGE 14
LTC4064 U W U U APPLICATIO S I FOR ATIO PROG pin. With no additional capacitance on the PROG pin, stability is acceptable with program resistor values as high as 50k. However, additional capacitance on this node reduces the maximum allowed program resistor. The pole frequency at the PROG pin should be kept above 500kHz. Therefore, if the PROG pin is loaded with a capacitance, C, the following equation should be used to calculate the maximum resistance value for RPROG: RPROG < 1/(6.
PAGE 15
LTC4064 U PACKAGE DESCRIPTIO MSE Package 10-Lead Plastic MSOP (Reference LTC DWG # 05-08-1663) BOTTOM VIEW OF EXPOSED PAD OPTION 2.794 ± 0.102 (.110 ± .004) 5.23 (.206) MIN 0.889 ± 0.127 (.035 ± .005) 1 2.06 ± 0.102 (.081 ± .004) 1.83 ± 0.102 (.072 ± .004) 2.083 ± 0.102 3.20 – 3.45 (.082 ± .004) (.126 – .136) 10 0.50 0.305 ± 0.038 (.0197) (.0120 ± .0015) BSC TYP RECOMMENDED SOLDER PAD LAYOUT 3.00 ± 0.102 (.118 ± .004) (NOTE 3) 3.00 ± 0.102 (.118 ± .004) (NOTE 4) 4.90 ± 0.152 (.193 ± .006) 0.
PAGE 16
LTC4064 U TYPICAL APPLICATIO S USB/Wall Adapter Power Li-Ion Battery Charger 5V WALL ADAPTER LTC4064 BAT 2 USB POWER IBAT 9 1µF VCC + Li-Ion CELL 1Ω 4.7µF 4 1k TIMER SHDN 8 SUSPEND GND NTC PROG 5 7 6 µC 3.74k 0.1µF 100mA/ 500mA 15k 4064 TA02 Li-Ion Battery Charger with Reverse Polarity Input Protection 2 5V WALL ADAPTER 8 4.7µF 4 LTC4064 VCC BAT VIN = 5V IBAT = 1A 1k PROG GND NTC 0.